1. Field of the Invention
The present invention relates to a charge accumulation read-out device of photosensitive detectors.
2. Description of the Prior Art
It is well known in the prior art to construct read-out devices which use charge accumulation of photosensitive detectors using a charge transfer shift register with parallel inputs and a series output whose stages have an increasing capacity depending on the direction of transfer of the charges. Such a device is shown in FIG. 1 where the photosensitive detectors are shown by the references D.sub.1, D.sub.2, D.sub.3 and D.sub.4 and the charge transfer shift register by the reference 1. Such a device is known under the name of "time delay integration" or TDI and it will be thus referred to hereafter.
In FIG. 1, an arrow indicates the relative direction of movement of the source 2 of radiation to be detected and of the detectors.
If N, detectors are used, the integration time is multiplied by a factor N provided that the information collected at the different detectors is summed in synchronism with the movement. The accumulation of the charges occurs automatically in the stages of the register whose capacity is increasing in the charge transfer direction, shown by an arrow in the shift register.
With the integration time multiplied by N and the read-out noise being added quadratically, a gain is obtained on the signal to noise ratio equal to .sqroot.N.
The problem which arises is that it is desirable to provide a read-out with charge accumulation for photosensitive detector matrices in which the detectors are distributed in several lines. Registers with increasing capacity prove to be too space consuming, perpendicularly to the charge transfer direction, to be able to be used without problems.
The present invention provides a solution to this problem and allows TDI read-out to be adapted to a photosensitive detector matrix.